The objective of this proposal is to investigate the microwave thawing process in frozen organic materials. Since 1968 this laboratory has investigated the effects of microwave radiation on rat skin, canine kidneys and gelatin molds. Radiation tolerance levels of cold cryoprotectant (DMSO) perfused canine kidneys have been established. Methods of thawing a frozen, cryoprotectant-perfused canine kidney have been evaluated by reimplanting the kidney in the dog's neck. To date, no kidney, after being frozen to a minimum of -40 degrees C and stabilized at that temperature, has retained sufficient function to sustain a dog's life although survival of the kidney components as glomeruli and tubules has been obtained. Renal pelvis, ureter and blood vessels survive consistently. Specifically, this investigation will measure the electrical properties of tissue in the frozen state, (2) develop and evaluate improved qualitative models of microwave heating of kidneys by analysis and computer simulation, (3) develop a uniform thawing schedule, employing more than one microwave frequency, for artificial organic gel kidneys which are similar in electrical and thermal properties to canine kidneys, (4) apply these techniques to live mammalians using rat skin and canine kidneys.